Plant Genome Stability and Change 2014
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| Year of publication | 2014 |
| Type | Appeared in Conference without Proceedings |
| Citation | |
| Description | Telomere erosion in Arabidopsis thaliana plants influenced by hypomethylating agents Telomeres, repetitive sequences forming complex nucleoprotein structures, are located at the end of linear eukaryotic chromosomes. Sequence of these minisatellite repeats is highly conserved through the eukaryotic organisms, TTTAGGG/CCCTAAA in most of plants. On the other hand, the length of telomeres is a variable parameter differing between organisms and even between different chromosomes in one cell. Telomeres play an essential role in the maintenance of genome integrity protecting chromosome ends against fusion, distinguishing natural chromosome ends from double-stranded breaks and compensating for the loss of DNA during the replication. Classically, telomeres are considered as heterochromatic structures. Recent report showed that telomeres of Arabidopsis thaliana model plant associated with both heterochromatin- and euchromatin-specific histone modifications (Vrbsky et al., 2010) and another study described that A. thaliana telomeres contained predominantly euchromatic marks (Vaquero-Sedas et al., 2011). We focused on the analysis of telomeres length and the level of methylation of telomeric cytosines in A. thaliana plants germinated in the presence of hypomethylating drugs zebularine and DHPA (dihydroxypropyladenine). These substances act by different ways; zebularine is able to incorporate to DNA, form a covalent bond with DNA methyltransferases and inactivate them, DHPA is an inhibitor of SAH (S-adenosyl-L-homocysteine) hydrolase and SAH a by-product of transmethylation reactions is a potent inhibitor of DNA and histone methyltransferases. In seedlings which were in direct contact with hypomethylating agent decreased level of methylated cytosines in telomeric and centromeric repetitive sequences was detected. In adult plants growing in soil without the presence of drugs, the level of cytosine methylation was almost comparable to that in control plants. Strikingly, considerable telomere shortening was observed in plants germinated in the presence of zebularine and DHPA. Telomere shortening was not correlated to changes of either telomerase protein subunit gene transcription or activity of telomerase, enzyme responsible for the telomere maintenance. Short telomere phenotype was transmitted to the progeny, which was not influenced by hypomethylation drugs. Possible mechanisms of telomere shortening and comparison of our data with similar experiments using A. thaliana methylation mutants met1, ddm1 and another model plant (Majerová et al., 2011) will be discussed. |
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